Download The second peak of the radial artery pressure wave represents

British Journal of Anaesthesia 92 (5): 651±7 (2004)
DOI: 10.1093/bja/aeh121
Advance Access publication March 5, 2004
The second peak of the radial artery pressure wave represents
aortic systolic pressure in hypertensive and elderly patients
A. L. Pauca1*, N. D. Kon2 and M. F. O'Rourke3
1
Department of Anesthesiology and 2Department of Cardiothoracic Surgery, Wake Forest University School
of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. 3Department of Medicine,
University of New South Wales, St Vincent's Hospital, Sydney, Australia
*Corresponding author. E-mail: [email protected]. Reprints will not be available from the author
Background. Simultaneous measurement of ascending aorta and radial artery pressure shows
that mean and diastolic pressures (DP) are in close agreement in normotensive adults, while
systolic pressures (SP) are not. However, in the aortic pressure wave, a second systolic peak
appears with increasing age and increases to represent the SP by age 32 yr, while in the radial
artery, a second systolic de¯ection appears by age 40 yr. We suggest that the second radial systolic wave, sometimes seen during radial arterial pressure monitoring in older hypertensives,
represents the aortic SP. We set out to evaluate whether the aortic and radial second systolic
peaks agree, and since doubts exist about the agreement between aortic and radial DP in elderly hypertensive patients, we also assessed that relationship.
Methods. We compared simultaneously recorded radial and aortic pressures from 21 anaesthetized adult patients using identical ¯uid-®lled pressure measuring systems.
Conclusions. The second radial pressure peak agreed with that in the aorta within a mean of
0.6 (SD 1.5) mm Hg. The difference between DP in the aorta and radial artery was ±1.4 (2) mm
Hg. The radial±aortic SP and pulse pressure differences were 5.9 (7.6) and 7.3 (7.6) mm Hg,
respectively. These results con®rm that when the radial artery pressure wave shows a ®rst and
second, or only a second systolic shoulder/peak (on the right side of the pressure wave), the
second represents the maximal ascending aortic SP, and that the radial and aortic DP are
equivalent, even in older hypertensive patients.
Br J Anaesth 2004; 92: 651±7
Keywords: age factors; arterial pressure, hypertension; heart, radial systolic pressure; heart,
systolic pressure differences
Accepted for publication: December 23, 2003
Since the work and oxygen demand of the left ventricle are
directly related to aortic systolic pressure (SP),1±4 and
myocardial oxygen supply might be impaired in some
patients,5 a measure of aortic SP would be of value during
major surgery. Radial artery pressure is usually monitored,
but this can be signi®cantly greater than aortic pressure in
normotensive adults.6 This may be because SP is taken as
the ®rst peak of pressure in the radial artery7 and by the
second peak of pressure in the aorta in adults over 32 yr.8
However, a second systolic de¯ection is noted on the radial
artery pressure wave by age 40 yr, which approaches the
magnitude of the ®rst by the eighth decade.7 Takazawa and
colleagues4 found that nitroglycerin equally reduced aortic
SP and the second systolic peak of radial pressure. This
suggests that the second radial artery de¯ection represents
aortic SP. The authors4 suggested direct comparison of
aortic and radial artery pressure waves to con®rm this, but
did not carry it out. There have also been concerns recently
about agreement between diastolic pressure (DP) measured
in the radial artery compared with the aorta in elderly
hypertensive patients.9
Using identical pressure systems to record pressure in the
aorta and radial artery, we assessed agreement between
aortic pressure and the second de¯ection of pressure in the
radial artery, and the agreement between DP in the radial
artery and aorta in older5 or hypertensive patients.
Ó The Board of Management and Trustees of the British Journal of Anaesthesia 2004
Pauca et al.
Table 1 Data from the 21 patients whose radial artery and aortic pressure
waves were compared. Data are mean (SD)
Control
Anaesthesia
Age (yr) (range)
64 (12) (41±87)
Weight (kg)
82 (17)
Height (cm)
170 (8)
Male/female
17/4
Ejection fraction (%)
53 (10)
61 (10)
60 (12)
Heart rate (beats min±1)
Core temperature (°C)
36 (1)
Arterial carbon dioxide tension (mm Hg)
39 (4)
Arterial oxygen tension (mm Hg)
236 (92)
Cardiac output (litre min±1)
4.9 (1.6)
Central venous pressure (mm Hg)
8 (2)
Diastolic pulmonary artery pressure (mm Hg)
11 (4)
Systolic pressure (mm Hg)
151 (19)
Diastolic pressure (mm Hg)
73 (13)
Mean pressure (mm Hg)
99 (12)
Pulse pressure (mm Hg)
78 (21)
Fig 1 (See Table 3.) Changes from A to B: noticeable decrease of systolic
pressure (SP) and second systolic peak, small decrease in diastolic
pressure (DP), and increase in heart rate and DP/SP ratio; C: moderate
decrease in pressures and blurred second systolic peak; D: small further
decrease of pressures; absence of second radial systolic peak; E: aortic
pressure simultaneously recorded with radial artery pressure; D: the aortic
systolic and pulse pressures are less than the radial, the radial DP/SP
ratio is less than the aortic. The DP/SP ratio was below 0.5 only in the
®rst recording (A); in E, the second aortic systolic de¯ection had
decreased below the ®rst, resembling that in young normotensives.8
Methods
The study was approved by the institution's Clinical
Research Practices Committee, and written informed consent was obtained from all patients before they were
considered for the study. We studied 45 patients undergoing
coronary artery surgery in whom we noted a second systolic
de¯ection in the radial artery pressure wave. The patients
were aged 41±87 yr, with 70% over 60 yr. Isolated systolic
hypertension (SP >140 and DP <90 mm Hg) was frequent
(78%).5 All were receiving antihypertensive medication
including angiotensin-converting enzyme inhibitors diuretics and b-blockers (atenolol or metoprolol). Before anaesthesia, we excluded patients with brachial SP differences of
5 mm Hg or more measured twice on both arms by
sphygmomanometry, those receiving nitroglycerin infusion,
and those in whom the radial artery was not cannulated
before anaesthesia. During anaesthesia, we excluded
patients in whom we could not see a second systolic peak
on the monitoring oscilloscope (Fig. 1). Thus, we compared
radial and ascending aorta pressure waves in 21 patients in
whom a second systolic peak was seen in the radial artery
following 60 (mean, SD 12) min of general anaesthesia,
chest surgery and heparin administration in preparation for
cardiopulmonary bypass (Table 1).
Before induction of anaesthesia, we cannulated a radial
artery and measured the pressure. We noted SP, DP and
mean arterial pressure, and whether the wave showed a clear
second systolic peak. Anaesthesia was established with
fentanyl, iso¯urane, midazolam and pancuronium for
muscle relaxation, and heparin 300 units kg±1 was given.
We recorded radial and aortic pressure simultaneously for
30±40 s at 60 (12) min after induction of anaesthesia. Both
pressures were measured through 5.1 cm, 20G Te¯on
catheters. The catheter in the ascending aorta was placed
pointing against the ¯ow at the aortic site chosen for
cannulation. Both catheters were attached to individual
high-pressure tubes, 91 cm long, 1.8 mm inner diameter
(exposed over their whole length to the same air temperature) and to matched Transpac7 IV transducers (Abbott
Critical Care Systems, Abbott Laboratories, North Chicago,
IL, USA). The pressure measuring systems were calibrated
statically to a mercury standard and kept meticulously
bubble-free. The natural frequency and damping coef®cients of the systems were measured by the ¯ush method at
the beginning and end of each recording in each patient,
ensuring a natural frequency at least 20 Hz and damping
coef®cient of at least 0.2.10 Both transducers were maintained at the same vertical level, checked by their equal zero
line display on the oscilloscope and recorder. The pressures
were printed on a high-®delity recorder (Siemens Medical
Systems, Iselin, NJ, USA) which was linear between 0 and
500 Hz. The recorder was calibrated so that 100 mm Hg v±1
output from the signal conditioner printed at 100 mm Hg per
652
Systolic pressure in old and hypertensive patients
Table 2 Radial (RA) and aortic (AA) pressures (mm Hg) and their
differences in the 21 patients whose pressure waves were compared during
anaesthesia. The RA±AA diastolic pressure difference, although small and
thus clinically non-signi®cant, is usually statistically signi®cant because the
aortic pressure is persistently greater than the radial pressure. Data are mean
(SD)
Systolic pressure
Second systolic peak difference
Diastolic pressure
Mean pressure
Peak pressure
RA
AA
RA±AA
pressure
differences
P value
129 (16)
123 (15)
62 (9)
84 (9)
67 (16)
64 (9)
85 (9)
60 (17)
5.9
0.6
±1.4
±0.1
7.3
0.002
0.1
0.003
0.8
0.0003
(7.6)
(1.5)
(2)
(3)
(7.6)
Statistics
Fig 2 Radial (R) and aorta (A) pressure waves recorded simultaneously
from a 62-yr-old patient, heart rate 50 beats min±1. The arrows indicate
the radial and aortic second systolic peaks. Radial and aortic pressure
waves were recorded simultaneously on two different channels of the
same recorder and then superimposed: the foot of the radial over the foot
of the aortic systolic rise (middle panel), placing their systolic peaks on a
similar time axis (X). As the zero and Y axis of both channels agree, it
was possible to compare the height of the aortic systolic peak and the
second radial systolic shoulders.
cm. This procedure included 50 mm Hg increments to 200
mm Hg per 2 cm for both radial and aortic recordings. Mean
pressure was obtained by electronic integration every 9.6 s.
Pulse pressure was calculated as the difference between SP
and DP. To measure the difference between radial and aortic
second systolic peaks, 10 s records from before the printed
SP, DP and mean pressures (recorded at 25 mm s±1 and 10
mm Hg mm±1) were copy-enlarged onto 50 or 100 mm s±1
and 5 or 2.5 mm Hg mm±1 transparent celluloid as well as
standard copy paper. These enlargements were superimposed on each other, so that the height of the radial and
aortic second systolic peaks and the alignment of the
gridlines on both recordings could be compared (Fig. 2).
The clinical management involved reducing and maintaining radial artery SP to about 120 mm Hg during
preparation for aortic cannulation (average 55 min); heparin
was given 4 min before aortic cannulation for bypass, and
the recordings were taken at this time. Clinical monitoring
included transoesophageal echocardiography and central
venous or pulmonary artery pressures to avoid low ®lling
pressures. Cardiac output was measured before the simultaneous radial and aortic pressure recordings.
In this study, the terms `elderly' or `older' refer to
patients over 60 yr. Above this age, SP continues to increase
in both normal and hypertensive patients, while DP
declines.5 Consequently, therapeutic decreases in SP
might enhance this age-related decrease in DP in elderly
patients. To assess this possibility, we used the ratio of DP
to SP, which expresses DP as a fraction of SP.
We used the paired t-test to compare radial and aortic
second systolic peaks, SP, DP, pulse and mean arterial
pressures. P<0.05 was considered signi®cant. We plotted
the difference between radial and aortic pressure against the
arithmetic mean of these values to display graphically both
the size of the difference between the radial and aortic
pressures measured and their maximal differences (Bland±
Altman plot).11 All data are expressed as mean (SD).
Results
No patients had unequal brachial arterial pressures out of 50
candidates for this study. However, three patients were
given i.v. nitroglycerin overnight and in two of these
patients, the radial artery was cannulated after induction of
anaesthesia; these ®ve patients were not included in the
study. In the remaining 45 patients, the radial artery pressure
had a second systolic peak before anaesthesia, which was
greater than the ®rst in 13, equal in 10 and lower in 22.
During the next 60 (20) min of anaesthesia and surgery,
when the aortic pressure could also be recorded, the second
radial systolic peak decreased, losing its de®nition in 24
patients (Fig. 1). In the remaining 21 patients (71% were
over 60 years), the second radial artery systolic peak kept its
de®nition, being higher than the ®rst in 4, equal in 4 and
lower in 13. In these patients, the radial±aortic second
systolic peak difference was 0.6 (1.5) mm Hg and nonsigni®cant, whereas the differences between radial and
aortic SP and pulse pressures were large and signi®cant
(P<0.01 and P<0.001, respectively) (Table 2). The aortic
DP and pulse pressures were 64 (9) mm Hg and 60 (17) mm
Hg, respectively, and heart rate was 60 (12) beats min±1
(Table 2).
Comparisons of SP, pulse pressure, DP and mean
pressures in the radial artery and aorta by Bland±Altman
plots11 showed similar disagreements (SP and pulse pressure) and agreements (DP and mean pressure) found in two
previous studies.6 12 The differences between the radial and
653
Pauca et al.
Table 3 One patient's data, illustrating changes in the radial artery (RA) waveform caused by anaesthesia in patients whose data were not used to compare
RA and aortic pressure (AA) second systolic peaks. A=15 min after induction of anaesthesia; B=35 min after chest incision; C=5 min later and 2 min after
administration of heparin 300 units kg±1; D, E=3 min later, when RA and AA pressure waves were recorded simultaneously
Time of
event
SP/DP
(mm Hg)
Peak pressure
(mm Hg)
DP/SP
ratio
Heart rate
(beats min±1)
Cardiac output
(litre min±1)
Diastolic pulmonary artery
pressure (mm Hg)
Second systolic
peak
A (RA)
B (RA)
C (RA)
D (RA)
E (AA)
164/78
125/70
96/55
95/52
81/52
86
55
43
43
29
0.48
0.56
0.55
0.55
0.64
49
74
71
76
4.7
5.0
4.6
4.7
13
11
11
12
>®rst
<®rst
unde®ned
absent
<®rst
Fig 3 Plot of the radial±aortic second systolic peak pressure difference
against their average. The differences and SD, rounded up to integers,
were 1 (2).
aortic second systolic peaks showed that all differences
®tted within the average difference 6 2SD (Fig. 3).
Figure 1 shows the changes in the radial artery pressure
waveform in one of the 24 patients excluded from the study
during anaesthesia. This patient was selected for this
illustration because he was one of three whose radial artery
pressure wave was distorted to the point of resembling the
aortic pressure wave when recorded at the beginning of
anaesthesia, and reverted to that seen in normotensive older
patients7 during anaesthesia. This patient was a 65-yr-old
hypertensive being treated with atenolol, who had coronary
artery disease and unstable angina but no other known
health problems. Control SP and DP (not shown in the
®gure) were 176 and 80 mm Hg, respectively, and the heart
rate was 52 beats min±1. Fifteen min after induction of
anaesthesia (panel A), the radial pressure showed a discrete
®rst systolic peak and a well-de®ned late systolic peak,
which was greater. Thirty-®ve min after chest incision
(panel B), the pressure wave had two systolic peaks, the
second slightly lower than the ®rst, but still identi®able as a
shoulder. Five min later and 2 min after administration of
heparin 300 units kg±1 13 (panel C), the second systolic
shoulder became a convexity, while SP and DP decreased.
Three min later (panel D), pressures were minimally lower
than in trace C, the second systolic peak was completely
absent and the inscisura was noticeably lower than its
counterpart on the simultaneously recorded aortic pressure
(panel E). Full details are given in Table 3. The most
obvious changes in Fig. 1 from panels A to B were the
decrease of the second systolic de¯ection, markedly reducing SP with minimal decrease in DP, the smoothing of the
postincisura de¯ection and the increase in heart rate.
Another noticeable change was the gradual loss of detail
in the radial pressure wave as anaesthesia proceeded, so that
by the time it could be compared with the aortic pressure
wave, there was little resemblance between the two, as can
be seen from panels D and E. The dissimilarity between the
radial and aortic pressures was common to all patients in
whom the second radial systolic de¯ection was blurred or
absent. In the aortic pressure, the second systolic de¯ection
represented SP in all 21 patients who had a clear second
radial systolic shoulder/peak and in 18 of the 24 in whom
the second de¯ection was replaced by a convexity.
Discussion
In this study, the comparison of radial and aortic pressure
waves in 21 patients shows that the second systolic peaks
agree within 0.6 (1.5) mm Hg. Thus, these results support
the view of Takazawa and colleagues4 that the second rather
than the ®rst component (shoulder/peak) of the radial
pressure represents aortic SP in adult patients. These authors
had compared the effect of nitroglycerin on the reduction of
the aortic maximal SP and the second radial artery systolic
peak in 24 adults, ®nding that this treatment reduced the
aortic pressure by 22 (13) mm Hg and the second radial
artery systolic shoulder by 24 (13) mm Hg, and that the
difference between these reductions was statistically insigni®cant. However, they had compared aortic pressure
recorded by microtip catheter, with aortic pressure derived
(through a process of averaging digitized pressure waves
and using elements of the fourth derivative to identify the
®rst and second systolic peaks) from radial pressures
recorded by applanation tonometry, and had not measured
DP in the radial artery. Therefore, they did not compare the
aortic and true radial pressure waveforms, and suggested
that analysis of the simultaneously recorded analogue aortic
654
Systolic pressure in old and hypertensive patients
and radial pressures would permit recognition of their ®rst
and second systolic de¯ections, and con®rmation of the
relationship between aortic pressure and the second radial
wave.4 Then, it would be seen that the lowering effect of
vasodilator treatment on the aortic pressure agreed with that
on the second radial wave. We have also derived aortic SP
from digitized radial pressure and transfer function technology in 62 anaesthetized patients.12 In 80% of these
patients the second radial systolic shoulder was absent, and
aortic SP was represented by the ®rst systolic de¯ection.
The difference between the measured aortic SP and that
derived from the radial artery was 0.0 (4.4) mm Hg, and well
within Association for the Advancement of Medical
Instrumentation guidelines14 for comparison of arterial
pressures with different methods of 5 (8) mm Hg.
However, the differences in individual patients ranged
between ±12 and 8 mm Hg. Thus, it seems that accurate
identi®cation or derivation of the aortic SP from radial
artery measurements is possible only if the treatment (e.g.
anaesthesia) does not decrease the second aortic systolic
peak below that of the ®rst, or the ability of the brachial and
radial arteries to transmit the aortic pressure. In the present
study, we compared simultaneous recordings of the aortic
and radial pressures, and found that the maximal disagreement between the aortic SP and the second RA systolic
shoulder was 2 in 19 patients, 3 in one patient and ±4 in one
of 21 patients (Fig. 3), con®rming that the second radial
systolic peak represents the aortic SP in older hypertensive
patients.
These data also con®rm that the agreement between the
aortic and radial DP in normotensive patients6 persists in
older hypertensives. Thus, the large overestimation of
directly measured brachial DP by cuff sphygmomanometry
(18 (12) mm Hg in patients with isolated systolic hypertension15) is not because of lower DP in the radial artery, but
the inability of non-invasive pressure measuring systems to
measure true DP in these patients.9
Representation of the aortic SP by the second radial
systolic peak implies that radial and aortic SP are equivalent
when the second radial systolic peak is equal to or greater
than the ®rst. Thus, the radial and aortic SP were equal in 23
of the 45 patients (51%) before, and in 8 of 21 (38%) during
anaesthesia. However, this study was not designed to assess
the effect of age or treatment on the aortic and radial SP, so
agreements of these estimates are provisional.
Estimates of the aortic SP and DP made from the radial
artery pressure wave allow rapid assessment of the effect of
reducing arterial pressure on aortic pressures in older
hypertensive patients, in whom aging and hypertension
increase the pulse pressure5 16 by increasing SP and
decreasing DP. Arterial pressure reduction by a treatment
may reduce pressures to a point where the reduction of DP
(a major coronary perfusion pressure factor) is relatively
greater than the reduction of SP4 9 (left ventricle work load).
In the radial artery, the aortic pulse pressure is the difference
between the second systolic de¯ection and DP, therefore
observing it before and early on during anaesthesia would
reveal whether the DP is greater than the pulse pressure for
any SP, as it normally is in young8 and middle-aged6
normotensive adults, and what effect anaesthesia has on
such a relationship. We incidentally noted in this study that
aortic pulse pressure was greater than DP in more than 50%
of patients before anaesthesia, and that anaesthesia
improved this relationship by decreasing the pulse pressure
in most patients (Fig 1, panels A, B and D), but had the
opposite effect in three patients. The present ®ndings may
help in evaluating the effects of anaesthesia (or any
vasoactive treatment) on the true aortic pulse pressure by
comparing the DP/SP ratio produced by such treatment with
known values in normotensive adults.6 8 This ratio estimates
DP as a fraction of SP and is 0.66 for awake normotensive
adults aged 35 (11) yr8 and 0.62 for normotensive,
anaesthetized patients aged 54 (12) yr.6 In Figure 1 and
Table 3, this ratio was 0.48 at the beginning of anaesthesia,
increased to above 0.56 during anaesthesia, and reached
0.64 when assessed in the aorta. However, in three of the 45
patients, it decreased from 0.48 to 0.3±0.4. Although there
are several possible causes of low DP in older hypertensives
(low heart rate, central venous pressure and/or stroke
volume),2 4 17 in these three patients a heart rate below 50
beats min±1 seemed to be the reason.
Analysis of the radial artery waveform alone has usually
been disappointing;18 however, simultaneous observation of
radial and aortic pressure waves has shown that the late
radial systolic de¯ection, which appears at age 40 yr and
continues increasing to reach the height of the ®rst peak by
the eighth decade,7 is closely associated with aortic SP.4
Aging and hypertension increase aortic SP by increasing the
second aortic systolic de¯ection19 20 and, coincidentally, the
height of the second peripheral systolic peak also
increases.1 4 Also, in older patients with arterial degeneration,19 the aortic pressure wave reaches peripheral arteries
with minimal distortion. Thus, there are persuasive reasons
for the presence of the second systolic shoulder/peak on the
radial pressure wave in older hypertensive awake patients.
In fact, the late tidal wave (second systolic peak) was
recorded for the ®rst time in hypertensive patients in 187221
using a mechanical sphygmograph±polygraph applied on
the radial artery at the wrist.
Recently, second systolic peaks from the left ventricle,22
ascending aorta and peripheral arteries have been recorded
with great ®delity using ¯uid-®lled clinical catheter systems
with frequency response of 11±12 Hz and damping coef®cient of 0.15.19 23 Additionally, diastolic and the second
systolic shoulder features of the radial pressure pulse are
included within 4±8 Hz.24 25 In contrast, signals with a high
frequency content such as rate of rise, ®rst peak and incisura
of pressure waves at heart rates of 120 beats min±1 require
pressure measuring systems with a frequency response
above 20 Hz.10 22 26 Therefore, we maximized the frequency
response of the systems used in this study to record
undistorted aortic pressure waves, which retain greater
655
Pauca et al.
details than clinically used radial pressure, as can be seen in
Figures 1 and 2. There are clinical states when the second
radial systolic de¯ection is poorly de®ned or absent in
awake patients.20 However, the most common cause of
blurred or hidden second radial systolic de¯ection is
pressure wave ampli®cation caused by the observer, for
example by changing a pressure wave displayed on four
separate channels to full-screen display where all pressures
show on the same scale. This manoeuvre increases the
amplitude of the displayed signal from 100 mm Hg cm±1 to
25 mm Hg cm±1, which straightens the rises and falls of the
pressure wave, reduces the separation between the ®rst and
second systolic peaks when they are at similar levels, and
changes the second shoulder into a convexity when the
second shoulder is lower than the ®rst. This manoeuvre
would have turned the second radial artery shoulder in
Figures 1 and 2 into poorly de®ned convexities. This effect
arises whether microtip1 27 or high-pressure ¯uid-®lled
catheter18 systems are used. We veri®ed this distorting
effect by amplifying digitized pressure waves from a
previous study 2±4 times.12
A practical approach to identifying second radial systolic
peaks is to consider the SP wave, from its foot to the
incisura, as three fractions. The ®rst systolic peak is located
on the ®rst fraction (0.08±0.12 s from the foot of the wave),
and the second on the third fraction on the right (approximately 0.25 s from the foot of the pressure wave).
easy, but can cause a low DP (e.g. below 40 mm Hg), which,
if ignored, could lead to myocardial ischaemia in elderly
hypertensives.29 However, the present ®ndings indicate that
invasive radial artery pressure monitoring provides SP and
DP measurements in close agreement with those in the aorta
of older hypertensives. Thus, anaesthetists can accurately
estimate aortic SP and DP using the radial artery waveform,
unlike epidemiologists and other clinicians who have to
guess, by sphygmomanometry, whether an arterial pressure
of 140/70 mm Hg is 140/70 or 140/30 mm Hg in the aorta.15
Whether reduction of arterial pressure from >160/<80 to
»120/>40 mm Hg by anaesthesia is the cause of
perioperative myocardial ischemia30 or of adverse outcomes
from coronary bypass surgery31 in patients with isolated
systolic hypertension remains to be investigated.
In summary, we found that the second radial artery
systolic peak, when visible, represents the maximal aortic
SP, and that the radial and aortic DP agree in hypertensives
and elderly patients.
References
Limitations
In this study, the pressure waves were compared after a long
period of anaesthesia and administration of a large dose of
heparin,13 which erased the second radial systolic peak in
more than half the initially sampled group. This was
unavoidable because this was the only chance to record
radial and aortic pressure waves concurrently with minimal
changes in clinical management. Use of paper recorder
instead of A/D conversion did not permit recording radial
artery pressures at 25 mm s±1 for long periods of time in all
patients because of the large amount of paper needed.
However, these limitations did not hinder the evaluation of
aortic SP and DP by the second radial systolic peak/shoulder
and the radial diastolic pressure, respectively.
Clinical implications
At present, the incidence of isolated systolic hypertension is
as high as 54% at 50±59 yr, and 87% of those aged 60 years
and over; diastolic hypertension prevails in a small number
of hypertensives below 50 yr of age.16 Systolic hypertension
is more dif®cult to control in older than in younger
patients.28 Thus, most treated older hypertensives may
present for anaesthesia and major surgery with SP above
140 mm Hg and DP below 80 mm Hg (85% of 45 in the
present group). Reduction of SP by anaesthesia to a
desirable clinical level (about 120 mm Hg) is usually
656
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